1. Changes of neuropeptides in the carotid body under systemic hypoxia.NPY immunoreactive nerve fibers in hypercapnic hypoxia are more than other hypoxia. VIP fibers in isocapnic and hypocapnic hypoxia are more than control. These results suggest that vascular expansion in the hypoxic carotid body is caused by VIP, and NPY is related to inhibition of vascular expansion in the hypercapnic hypoxic carotid body. (Adv. Exp. Med. Biol. 536:611-617, 2003.)2. The time course of changes of neuropeptides in the hypoxic carotid body.SP, CGRP and VIP fibers in the carotid body increase 4 weeks after hypoxic exposure, but SP and CGRP fibers decrease 8 weeks after exposure. NPY fibers show no changes. These result suggest that adaptation of neuropeptides in the carotid body to hypoxia is completed 8 weeks after exposure.(Histol. Histopathol. 18:409-418, 2003).3. Morphological changes of the carotid body after the termination of hypoxic exposure.The size of the carotid body under hypoxia is diminished after the termination of hypoxic exposure.(Histol. Histopathol. 19:1133-1140, 2004.)4. Changes of neuropeptides in the rat carotid body after the termination of hypoxic exposure.NPY fibers increase one week after the termination of hypoxic exposure, and VIP fibers decrease at the same time. It is suggested that some neuropeptides are related to morphological changes of the carotid body with arterial O2 tension. (Histol. Histopathol. 19:1133-1140, 2004.)5. In situ hybridizationChanges of mRNA of neuropeptides in the trigeminal and sphenopalatine ganglia with hypoxic exposure have been observed using in situ hybridization.